- with readers working within the Environment & Waste Management industries
On May 18, 2026, EPA proposed two significant changes to the federal drinking water regulations for PFAS (per- and polyfluoroalkyl substances), commonly known as “forever chemicals.” One would rescind the Biden-era standards for four categories of PFAS, and the other would extend the time for qualifying water systems to comply with existing standards for PFOA and PFOS by up to two additional years. Both proposals carry significant implications for regulated entities and environmental liabilities, yet both also face likely legal challenges—underscoring that the PFAS regulatory landscape continues to remain unsettled.
Background: The 2024 PFAS Drinking Water Rule
EPA finalized the PFAS National Primary Drinking Water Regulation in April 2024. The rule established legally enforceable maximum contaminant levels (MCLs) of 4.0 parts per trillion (ppt) for PFOA and PFOS, and 10 ppt for PFHxS, PFNA, and HFPO-DA. It also regulated certain mixtures of PFHxS, PFNA, HFPO-DA, and PFBS through a hazard-index approach that measured each compound’s concentration relative to its health-based threshold and summed the results, with compliance achieved if the combined score did not exceed 1.0. The rule required public water systems to comply with these MCLs by April 2029.
Proposal One: Rescinding Limits for Four PFAS Categories
EPA’s first proposal would rescind the regulatory determinations and related drinking water requirements—including the 10-ppt MCLs—for PFHxS, PFNA, HFPO-DA, and hazard-index mixtures of those three PFAS plus PFBS.
EPA says the proposal is “solely” intended to correct what it characterizes as an “unlawful process” under the Safe Drinking Water Act (SDWA)—specifically, that EPA erred by issuing rules for these PFAS “without first completing the regulatory determination as a necessary prerequisite to rulemaking.” The agency states that it may evaluate additional PFAS in drinking water for future regulation after final action.
Proposal Two: More Time for PFOA and PFOS Compliance
EPA’s second proposal would keep the federal PFOA and PFOS MCLs in place while creating an option for drinking water systems to seek two additional years, until 2031, to comply. EPA describes the proposal as a “federal exemption framework” for systems in states, territories, and Tribes that have not obtained primary enforcement authority (also called “primacy”) for the PFOA and PFOS MCLs. EPA frames the extension as a practical implementation measure, pointing to long construction timelines for treatment facilities, workforce challenges, financial limitations, and availability of water-quality data to inform capital improvement decisions.
Systems that receive exemptions would still have to meet monitoring and reporting requirements on the timelines established in the 2024 rule, and those with PFOA or PFOS sample results at or above 12 ppt would also have to take short-term mitigation actions during the exemption period.
Implications for Regulated Entities
For public water systems, the central near-term takeaway is that PFOA and PFOS remain regulated at 4.0 ppt, even if qualifying systems may obtain more time to achieve compliance. For systems already planning capital projects, treatment procurement, or source-water changes, the proposed extension may provide flexibility but not a complete pause, because monitoring, reporting, public notice, and potential interim mitigation obligations would continue.
For manufacturers, site owners, potentially responsible parties (PRPs), and parties conducting environmental due diligence, the proposals add another layer of uncertainty rather than eliminating PFAS risk. As we noted when EPA first proposed the standards in 2023, MCLs often become applicable or relevant and appropriate requirements (ARARs) at CERCLA sites. This means PFAS drinking water limits can affect cleanup expectations for groundwater contamination. EPA’s proposal to allow two-year extensions for compliance with the PFOA and PFOS MCLs would provide no relief to CERCLA PRPs; the MCLs remain in place and thus would also remain likely ARARs at Superfund sites. On the other hand, rescission of the other PFAS standards, if finalized, could eliminate PFHxS, PFNA, HFPO-DA, and hazard-index mixtures of those three PFAS plus PFBS as a driver of CERCLA cleanup standards. Both rules face likely legal challenges, however, so the applicable standards remain uncertain for now.
Further adding to the complexity of the PFAS regulatory landscape, several states have adopted their own PFAS drinking water standards. Depending on how such state standards have been adopted and their regulatory enforceability, state standards may also be ARARs that can drive Superfund site cleanup decisions. Meanwhile, EPA has said it plans to issue technology-based effluent limits and pretreatment standards for certain PFAS-discharging industries, including chemical manufacturers—potentially shifting PFAS control obligations upstream in the long run.
Comment Period
EPA will accept written comments on the proposed rules for 60 days after publication in the Federal Register, and it has scheduled a virtual public hearing for July 7, 2026.
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